1. U.S. Department of the Interior U.S. Geological Survey Sustainability of Ground-Water Use in the San Pedro River Basin, Cochise County, Arizona James Leenhouts, Ph.D. IAEA/GEF IW Learn/USGS Aquifer Exchange April 19, 2007

2. The Upper San Pedro Basin  San Pedro River flows north from near Cananea, Mexico to Gila River  4,480 km 2 area above Tombstone gage  1,810 km 2 in Mexico  2,670 km 2 in U.S. Tombstone gaging station Fort Huachuca

3. The Problem: Competing Assets  The San Pedro’s riparian system (SPRNCA)  Federally protected in 1988  One of shrinking number of free- flowing perennial rivers in the Southwest  The human community  National asset: Fort Huachuca  Growing population  Great climate, beautiful environs

4. Streamflow at Charleston Pumping Streamflow Fort Huachuca

5. Zero flow at Charleston, Summer 2005

8. Investigations  Geohydrologic studies  Improve the conceptual model  Detailed investigation of physical system  Synthesis in ground-water model  Riparian water needs studies  Multidisciplinary study  Related hydrologic variables to riparian condition  Quantified riparian ET

9. Geohydrologic Studies  Water levels  Streamflow  Aquifer storage change - microgravity  Geophysical exploration  Unsaturated zone flow  Stream temperature monitoring Lacoste and Romberg Model D Relative-gravity meter

10. Investigations Network

11. W E T L A N D S S T R E A M BEDROCK ET RECHARGE CURRENT CONCEPTUAL GROUND-WATER FLOW SYSTEM Spring limestone EPHEMERAL STREAM RECHARGE EPHEMERAL STREAM RECHARGE EASTWEST

13. Riparian Water Needs Investigation  Three components  Hydrology  Ecology  Evapotranspiration

14. Riparian Condition Class  Relates hydrology to ecology  Provides science to inform policy

15. The Mandate: Sustainable Yield  Stipulated by Congress  Not safe yield --> pumping = recharge  Sustainable Ground-Water Yield  “…the development and use of ground water in a manner that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.”

16. The Players  Upper San Pedro Partnership  21 local, state, federal, and non- governmental agencies  Goal is to identify and implement solutions to assure reasonable water supply for the river and the people  AZ congressional delegation  Other groups

17. Reservoir Analogy No Pumping Safe Yield Sustainable Yield

18. Initial Criteria for Sustainability  Unacceptable consequences:  The riparian system ceases to function  Unavailability of water causes Fort Huachuca to close

19. Sustainable yield  How much water:  Do the people need?  Does the riparian system need?  Temporal effects  Spatial effects  Climatic effects

20. Ground-Water Budget

21. Sustainable yield – initial goal An Aquifer-Storage Approach

22. Sustainability – defined spatially  Define indicators and thresholds  Indicators – variables that inform status  Thresholds – markers beyond which sustainability fails EnvironmentSocioeconomic IndicatorThresholdIndicatorThreshold Ground-water levels – regional aquifer ??? Streamflow ??? Spring discharge ??? Ground-water levels – alluvial aquifer Defined by water- needs study ??

23. Assessing Progress = Monitoring  Water budget aspects  Tabulation of pumping  Continued refinement of inflow and outflow values  System-response aspects  Water levels  Microgravity  Spring and stream discharge  Vertical gradients

24. Sustainable Yield – Adaptive Management  Iterative interaction  Management Action  Monitoring  Analysis

25. Science Informing Policy  Spatial definition of ground-water management  “Capture map”

26. Semiarid: Only half of the residents drive camels Questions?

27. Reaching the Goal  Broad categories of water management measures:  Conservation  Growing population  Recharge  Needs source of water  Importation  Potential legal issues

28. Perennial Intermittent Stream gage

29. Who, What, Where, When, How?

30. Interaction of Multiple Factors

31. Annual Section 321 Reports  See the 2004 Section 321 report at: http://water.usgs.gov/Section321.2004_050705.pdf

32.  Sustainability:  “…the development and use of ground water in a manner that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.”

33. Outline  Introduction to basin – talk about SPRNCA – usual superlatives, Fort, Cities  The issues – declining streamflows, zero flow.  Discussion of the players  Capture  Description of work done – model, water needs.  Sustainable yield goal – Section 321  Status of water budget – include reservoir analogy to sustainable yield  Science to policy section  Section 321 reports  Capture maps  Level change maps  Gravity maps